1. Field of the Invention
The invention relates to an acid yellow dye and a method for using the dye. Specifically, the invention relates to an acid yellow dye for use with dyeable polyamide polymers or "nylon" materials and a process for using the dye on polyamide fibers.
2. Description of Related Art
Synthetic dyes and dyestuffs have gained substantial commercial value for dying synthetic materials such as polyesters, polyamides, and cellulose ethers such as rayon. One class of synthetic dyes that has substantial market demand includes greenish-yellow dyes for polyamide materials. These dyes have great value for use in dyeing carpet and apparel.
Dyes used to color carpet and apparel materials must have good light fastness and good wash fastness as well as other characteristics. Standard tests exist within the industry to evaluate these characteristics of a dye.
The term "light fastness" refers to the ability of a dye to resist degradation from light, especially sunlight. The term "colorfastness to light" is sometimes used as a synonym for the term "light fastness." A standard for testing and rating light fastness is performed by exposing a dyed material to a light source of known spectrum and power and comparing the exposed, dyed material to a color standard after an exposure period.
The term "wash fastness" refers to the ability of a dye to resist degradation or removal from a substrate upon exposure to repeated washings. Standards for wash testing are also established. One such test is the "2A Wash Test" of the American Association of Textile Colorists and Chemists. This test washes a dyed material in a known concentration of a standard detergent.
The increased popularity of synthetic fiber materials in the 1960's and 1970's resulted in the development of standards for evaluating other dye characteristics for these fiber materials. The industry developed tests to compare dye compatibility so that one material can be dyed simultaneously by a plurality of dyes.
An article by Beckmann et al., "Practical Significance, Theory and Determination of Compatibility of Dyes on Synthetic-Polymer Fibres," Journal of the Society of Dyes and Chemicals, Vol. 88 (October 1972): 354-60, describes the "compatibility value K." The compatibility value K is essentially the product of the diffusion coefficient and the affinity of the dye. A dye of a lower K value "exhausts" before a dye with a higher K value.
An article by Otten, "Combination Indices for Acid Dyestuffs in Polyamide Dyeing," Farben Review, No. 21 (1972), describes parameters for dyeing procedures using a combination of dyes with different characteristics. This article describes the dye characteristics of combinability, levelness, and rate production of acid dyes on polyamide fibers. The absorption rate of acid yellow dye is discussed in combinations with acid blue and acid red dyes of different absorption rates.
The industry developed procedures and equipment for simultaneously applying a plurality of dyes onto a material. Trichromatic dye systems were developed for use in rapid, continuous dyeing applications. Such applications are often performed by high-speed, computer-controlled equipment.
U.S. Pat. No. 4,579,561 to Rowe et al. discloses a process for trichromatic dyeing of polyamide fibers. This patent discloses a system including an acid red component, an acid blue component, and an acid yellow component. Each of the dye components has compatible performance characteristics with the other dye components.
U.S. Pat. No. 5,234,467 discloses azo dye mixtures and their use for dyeing natural and synthetic polyamide fibers. The patent discloses yellow or orange dyes that are suitable in combination with other dyes. The disclosed dyes have very good compatibility for trichromatic dyeing systems.
The compatibility of individual dyes in a trichromatic or similar dye composition is determined in part by the respective "exhaust rates" of the dyes on the intended substrate material. Unlevel dyeing occurs when one of two or more dyes "strikes" too fast while a "sleeper" dye continues to exhaust. Dyers require a selection of dyes in order to develop combined dye compositions wherein the rate compatibility of the dyes is complementary for the process parameters required to dye a particular material.
Some acid yellow dyes exhibit undesirably rapid striking on polyamide fibers in dye compositions with an acid blue dye and/or an acid red dye. Dye compositions containing acid yellow dyes often fail to provide an "on tone" color on a polyamide fiber material. The "migration" characteristics of a dye on a fiber also affect the tone of the color on a polyamide fiber. Leveling agents are often required to compensate for differences between different acid dyes used in a dyeing process.
The industry requires an acid yellow dye having good light fastness and other properties for dyeing polyamide fiber. Also, the industry lacks acid yellow dye compositions wherein rate characteristics can be selectively altered to provide compatibility in a di- or trichromatic dye composition with acid blue dyes and/or acid red dyes. Additionally, the industry needs an acid yellow dye that reduces or eliminates the need for leveling agents in the dyeing process, which is advantageous for the dye houses in that it contributes to a reduction in the number of chemicals they need to use.